Leviticus 6:9-10

9“Command Aaron and his sons: This is the law of the burnt offering; the burnt offering itself must remain on the altar’s hearth all night until morning, while the fire of the altar is kept burning on it.

10The priest is to put on his linen robe and linen undergarments. He is to remove the ashes of the burnt offering the fire has consumed on the altar, and place them beside the altar.